Directory Synchronization does not bring over the msExchArchiveGUID attribute. Other attributes not migrated include:
mailNickname
msExchArchiveGUID
msExchArchiveName
msExchArchiveQuota
msExchArchiveWarnQuota
msExchELCMailboxFlags
msExchMailboxGuid
msExchMobileAllowedDeviceIDs
msExchMobileMailboxFlags
msExchPoliciesIncluded
msExchRecipientDisplayType
msExchRecipientTypeDetails
msExchRemoteRecipientType
msExchTextMessagingState
msExchUMDtmfMap
msExchUserAccountControl
msExchVersion
msExchWhenMailboxCreated
proxyAddresses
targetAddress